See the OSHA page at http://www.osha.gov/dts/hib/hib_data/hib19880520.html

"The Dallas Regional Office has brought to our attention a potential serious hazard existing with the use of polyvinyl chloride (PVC) plastic pipes for transporting compressed gases in above ground installations. An employee in a Texas plant was injured recently by a rupture in a PVC compressed air line. Plastic projectiles from the point of rupture caused lacerations of the employee's hand. This is noteworthy because the Plastic Pipe Institute, in its Recommendation B dated January 19, 1972, recommends against the use of thermoplastic pipe to transport compressed air or other compressed gases in exposed plant piping.

Furthermore, sections 842.32, 842.43 and 849.52(b) of the American National Standards Institute/American Society of Mechanical Engineers (ANSI/ASME) B31.8-1986, Gas Transmission and Distribution Piping Systems Standard, limit the operating pressure of plastic piping distribution systems to 100 pounds per inch (psi) and prohibit the installation of such systems above ground except where ". . . the above ground portion of the plastic service line is completely enclosed in a conduit or casing of sufficient strength to provide protection from external damage and deterioration.""

See the page referenced for more info.

You are saving pennies at the risk of a life. 

Back to the original topic, I don't know about pex.  I don't think it is designed for that much pressure.  There is a flexible line designed for air pressure.

My dad had it (plastic) for years, came home one night to the air compressor running.........Am glad no-one was in it when the line blew.......Ive never seen pvc blow, but Ive seen the tiny peices it creates after it blew, and Ive seen a potato shot out of a pvc air compressor selenoid hookup............ Put the two together and it wouldn't be good.

All Im saying is, I won't come in your shop when your 30 year old pvc lines are pressurized.  No offense.

Looks to me like that's at 180 degrees F. If you bring the temp down to 73 aquapex should be safe for 160psi. That said, you can buy the 1" Pex:Alum:Pex rated for 200PSI at 73*F for $450 for a 300 foot roll. I'd like to see someone buy 300' of 1" copper pipe for that kind of money.

I do not think you can go with 73 degrees on the air line.  An air line will fail a hydraulic hose in about four years due to heat. 

Also need to consider the oil....not sure where polyethylene stands there. 

I dunno halfbake,

Why not go to runnings, buy a bunch of rubber airline hose, clamp it to the wall with quick couplers T'd into wherever you want.

Last I checked the rubber was allot cheaper, and won't sweat like metal.

Just a thought,

Good luck

Ya know, now that you say that I think we got PVC air lines in the new shop in Brookings.  I have never realy looked at it, I only worked in it a couple times and only welded when I was there.

In Flandreau we have all iron lines and one line run with plastic truck air line(cause we had it) and because it had to go up and over and around and down and under and up.

I know that ALL our buildings have had walk throughs, so the shop must have passed.

I will have too make a phone call tomorrow.

I was quite surprised to see a local manufacturer that had PVC air lines run all around their building. I would surely think OSHA visits them periodically. We went with schedule 80 pvc for some safety factor (8 or 10 years ago???). It is quite a bit thicker and rated for higher pressure. I don't know that I would do it again and would not recommend it to anyone else but we have not had any problems. I went to the 1" sched 80 after talking to a number of shops running pvc that used the air a lot more than we do. The one shop did have a failure every couple years but it had always been within a few feet of the air compressor where the air is hot. The PVC would split where the hot air came out of the compressor. PVC looses rated capacity pretty quick as it warms up. That is why I went to the sched 80.

I did ours before all of the posts here on AgTalk and after visiting a lot of places using it. Since then from what I have heard on here I probably would not do it again, but on the other hand I also have no plans on changing it in the near future. Maybe someday. PVC does get brittle with age, especially if exposed to sunlight. We learned this in our turkey barns. First couple years the lines could freeze up when we had no birds in the buildings without much damage. After the pipes got a few years old any freeze at all would bust a bunch of them. Also you can take a new piece of pipe and cut it easily with the standard PVC slicer type cutter. If you have a piece that is several years old it will only shatter it - better use a saw rather than a cutter if an old piece has to be used again.

John

I wonder about putting something u-shaped *like* guttering (but heavier) over your lines for piece of mind in case they eventually fail.  I suppose the problem would be that it's liable to cost more then simply replacing them.

The thought ocoured to me of covering it somehow but like you say, might be easier and just as cheap to just replace it. I'm not fond at all of steel. Putting it in doesn't bother me, it is the moisture/rust factor. Like one other poster on here stated, he observed one that had rusted half way shut. I know on steel water pipes with our well water some fittings can seal virtually shut in 10-15 years with rust. Seems to do it at the junctions the worst. Air would not do it that bad but the rust flakes in air tools I would not like. Dont think it would be any better for lubricant as the water and probably a lot worse. Steel may be the least of evils. Rigid copper sounds good, don't know if it would have corrosion problems.

We have a good size water seperator on the outlet of our tank that we drain regularly and have an auto drain on the tank itself but still get a lot more water in the lines than I like. If we were using only small amounts of air, giving it time to cool in the tank, I think the tank would keep most of it. When we get to blowing a combine off or something that takes tons of air and the hot air gets to the lines, there is where the water starts condensing, as it cools. 

John 

That makes a lot of sense. I am probably putting too much emphasis on rust. Probably not that big of an issue.

John 

Seems like we always have way more water then it seems like we should.  Compressor is breathing cold air, then blowing into second 80 gallon compressor tank, then into 1 1/4" pipe that goes to 2" before it goes 15' up the wall, with a drain at the bottom,  then 2" for about 40' on the ceiling before the first down, which again has a drain a foot or so below the couplers.   There are several other drains around the shop, and every one of them will have moisture most any time you drain it.

I worry more about the tanks rusting and failing then the pipe.  I would have never worried about tanks at all before learning from people here...now I have a tendancy to dump the tanks if I'm going to be working in the mechanical room where they are located for very long.

We have an auto dump on our tank. They work good but ours has worn out (at least seals dont seem to help it) after a few years though. They dump off kind of like an air dryer on a truck, when the pressure rises then falls.

Which reminds me of a thought I once had and lost - why not use a truck style drier? I guess the problem might be needing several of them in parallel  to match a large capacity compressor and a 12 volt source to operate them. Maybe replace the dessicant once a year. They do seem to work good though.

john 

Our first compressor has an automatic dump valve which dumps a half pint or so every time the compressor starts or stops. The second one (basically a holding tank, it only comes on if the first one can't keep up) has a manual drain valve on it.

The welding company I think we both use supplied us "best" filter setup for the plasma.  It does seem to have helped our consumable problem a lot....unlike the "best" one from the welding supply we used before, or the 'best' one from the air compressor place.   I just told him to get me something which would work....didn't care what it cost if it worked...couldn't stand to keep burning up $50 bills every time the plasma cutter was turned on.

I made the suggestion below in another post to put drops down below the outlets to trap water. Another thing I would have liked to do and thought about it but didn't do it but now wish I had..........that statement ought to make some English teacher just sick.............run the main lines with a slope like you would a concrete floor that you want water to drain off. Then put a ball valve drain at the lowest point. Fortunately our plasma cutter is on the far side of the shop and the air is the driest by the time it gets there but a couple of outlets near the compressor you can literally put an air gun on and see water spew out with the air for a minute or more. I try to get my guys to not use air tools on these outlets. I ran all my main lines flat because that was the easy way to attach them to a siding board that the tin hangs on. I should have made some provision to put it on a slope. I did finally put a BIG ball valve (1" same as line) at the lowest place where the compressor line attaches to the compressor and a valve on the compressor. This way I can shut the compressor tank valve and open the drain valve and the air will reverse flow back out the line and clean a lot of the water out. It helps. We have a 1" water separator on the outlet of the tank that works but it still doesn't get it all. We must have 20 or 30 gallon of capacity in the lines alone because opening that one inch ball valve wide open takes quite a few seconds to empty the line.....better have ear plugs in also. It'll blow a cup or two of water out after a few weeks time.

Air quality makes a big difference on air tool life and ours is not as good as I would like. Water makes a lousy lubricant for impact wrenches.

John

Yes we were warned of that when we got ours so we actually have two driers ahead of ours (one toilet roll style then one with replacable desiccant after it) and have had no problems. In fact we rarely have to replace the brown roll in the one or the dessicant in the other. The line to the far side of the shop must be relatively dry. That reminds me, I need to remind the shop guys NOT to plug the plasma into the outlets near the compressor if they take it to that side of the shop - or we will be replacing drier elements.

John

I believe the PEX I buy @ home-improvement type stores for the purpose of adding runs to our air line in our shop is approved for "gas". I assume they mean like LP or natural...not the liquid kind for our gasoline engines. I believe I recall the rating being 150#.

I also try to think about this a little bit. I assume that whoever gave it that rating to hold a highly flammable gas (LP) inside a house probably used a 100x fudge factor..maybe not that much, but probably a lot. So-I figure that carrying a non-highly-flammable gas like compressed air isn't that big of a deal.

So-after having read here a few yrs ago about all the multitudes of shrapnel explosions from pvc that people had personally suffered (no photos??) I decided PEX might be better. I try to test stuff when I can. So, I took a 1' piece of pex, capped on one end (Pex fittings) & hooked it up to 150# air line & compressed it. Then I put a ball valve on the end & closed it off thereby trapping the air. Then I laid the pex on an anvil & started beating the hell out of it trying to get it to explode. I think I read here that many of the personally encountered pvc explosions (vs the ones guys heard about) happened when someone hit a pressurized pvc line somehow. So-I figured the beating test was important. I beat that pressurized pex 'til it had no body left anymore....but it still held the pressure. I then put it in a vise & kinked it & beat on it some more, trying to get it to rupture @ the kink. I finally got tired of of beating/kinking the thing & called it "safe enough for ME".

I personally recommend only using OSHA recommended products & installation procedures in their private farm shop.